Field of the Invention
This invention relates to producing liquid fuels, specifically to in-situ or ex-situ coal to liquid conversion.
Background of the Invention
Coals can also be converted into liquid fuels like gasoline or diesel by several different processes. In a developing commercial process, the coal converted into a gas first, and then into a liquid, by using the Fischer-Tropsch (FT) process. In the FT process, an indirect route, coal is first gasified to make syngas, a purified mixture of CO and H2 gas. Next, FT catalysts are used to convert the syngas into light hydrocarbons, like ethane, which are further processed into refinable liquid fuels. In addition to creating the fuels, syngas can also be converted into methanol, which can be used as a fuel, or a fuel additive.
Alternatively, the coal may be converted directly to liquid fuels via hydrogenation processes. For example, the Bergius process, in which coal is liquefied by mixing it with hydrogen gas and heating the system. Several other direct liquefaction processes have been developed, such as the Solvent Refined Coal (SRC) processes, which has spawned several pilot plant facilities. Additionally, dried, pulverized coal mixed with roughly 1 wt % molybdenum catalysts may be hydrogenated by use of high temperature and pressure synthesis gas produced. However, the syngas must be produces in a separate gasifier.
However, these coal to liquid fuel processes involve the mining of the coal from the ground. As is well documented, coal mining is a hazardous process, and many mines are forced into closure prior to the removal of all useable products. Further, those mines that are operated safely leave behind large columns of coal to support the ceiling and coal residues in the mine walls. These sources of coal represent a significant amount of energy that is left abandoned by mining operations. Further, these untouched resources may be converted to liquid fuels for transportation purposes. As such, there is a need in the industry for the removal of abandoned, low quality, or residual coal from mining operations, for use in the coal to liquid production.